1. Field of the Invention
The present invention relates to electronics and, more specifically, to Class AB amplifiers.
2. Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
Class AB amplifiers offer a tradeoff between the linearity of Class A amplifiers and the power efficiency of Class B amplifiers. Class AB amplifiers are widely used as an output stage to provide a sufficiently linear rail-to-rail output signal with good power efficiency.
FIG. 1 shows a schematic circuit diagram of a conventional Class AB amplifier 100 that receives an input voltage signal VIN and generates an amplified output voltage signal VOUT to drive a load current iL across a load resistor RL. In amplifier 100, transistors M1 and M2 are in a complementary source-follower configuration, where M1 is a p-type (e.g., PMOS) source-follower, and M2 is an n-type (e.g., NMOS) source-follower. This complementary source-follower configuration needs a supply voltage Vdd of at least 2*Vgs+2*Vdsat to operate properly, where Vgs is the gate-to-source voltage and Vdsat is the difference between Vgs and the threshold voltage Vth for the transistor devices used to implement amplifier 100. As such, amplifier 100 is not suitable for low-voltage supply scenarios. Furthermore, it has relatively high power consumption.